The following definition for evidence-based public health practice that is currently being used by some in the New Mexico Department of Health.
|1 Examples of Evidence-Based Practice|
2 Strength of Evidence
3 Where do I find Evidence-Based Practices?
4 Research Methodologies
Examples of Evidence-Based PracticeHere are two examples that may help in understanding what evidence-based means:
EXAMPLE ONE (POLICY)
- An intervention (an alcohol tax to reduce alcohol consumption and driving while intoxicated) is proposed. A city passes this law.
- An independent evaluator tracks rates of DWIs over a year, once the tax is imposed.
- An evaluation report, published in a peer-reviewed journal, indicates a reduction in DWI's following the tax increase.
The "evidence" is the reduction in DWI, and in this case, the evidence suggests that the intervention was effective. Although another aspect to consider is whether there were there other factors that could account for the reduction in DWI (e.g., road checks, public education campaign).
EXAMPLE TWO (PROGRAM)
- An intervention (a series of policies and workshops designed for a school to reduce bullying among students) is proposed. A school district uses it for a year - implementing policies and workshops for teachers, parents, and students in grades 3-8.
- An independent evaluator tracked the incident reports related to bullying in grades 3-6.
- An evaluation report, published in a peer-reviewed journal, indicates that bullying reports did decrease in grades 3-6.
The "evidence" in this example is the decrease in bullying following the intervention. Other factors to consider: where was the school (in the USA or Canada, in a wealthy or low income part of town?) Since the evaluation was conducted with students in grades 3-6, can one assume the intervention will work with the older, middle-school, students?
Strength of EvidenceAs you might imagine, not all evidence is created equal. Here is a short list of what to look for in evaluating evidence for best practices in public health. The most desirable interventions are those that maximize each of the following criteria.
|Characteristics of the Evidence:||Good||Poor|
|REPLICATED IN MULTIPLE STUDIES||WHAT STUDIES?|
|CAUSAL, RANDOMIZED, CONTROLLED STUDY DESIGN||ANECDOTES, CASE STUDIES, SPECULATION|
|STUDY POPULATION SIMILAR TO LOCAL POPULATION||STUDY POPULATION DIFFERENT FROM LOCAL POPULATION|
|Characteristics of the Intervention:||Good||Poor|
|SHORT INTERVAL (LESS THAN 4 YEARS)||INTERVAL LONG OR UNKNOWN|
|LONG-LASTING EFFECT||EFFECT FADES QUICKLY|
Additional criteria may also be relevant, but the criteria above will help as you evaulate the evidence in favor or against potential interventions.
Where do I find Evidence-Based Practices?These Websites, below, also contain useful guidance on specific evidence-based interventions.
- The Community Guide
- CDC National Prevention Information Network (NPIN)
- SAMHSA's Evidence-based Programs and Practices Resource Center)
Research Methodologies for Cause-and-effect RelationshipsThese three criteria must be met for a study to demonstrate a cause-and-effect relationship:
- Observed Statistical Association. There must be some statistical evidence of association between the cause and the effect.
- Time Precedence. The cause must occur first, followed by the effect.
- Rule out Alternative Explanations for the Association.
The last criterion is the most difficult to satisfy. A "true experiment" is a study design that is intended to rule out alternative explanations.
By definition, a "True Experiment" has the following characteristics.
Without a true experiment, it is very difficult to establish a credible causal relationship.
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